codope opened a new pull request, #12993:
URL: https://github.com/apache/hudi/pull/12993
### Change Logs
When reading column statistics for Decimal fields from the metadata table,
the unwrapped decimal values are incorrectly handled. Specifically:
- **Type Loss in Unwrapping:**
The `tryUnpackValueWrapper` method was matching a `BytesWrapper` before a
`DecimalWrapper`, causing values written as `DecimalWrapper` (which are
actually decimals) to be interpreted as raw bytes.
- **Incorrect Deserialization:**
In the `deserialize` method, the decimal conversion was not robust enough:
- It only handled the case where the unwrapped value is a `ByteBuffer`.
- It did not enforce the correct scale/precision when the value was
already a decimal (either as a Scala `BigDecimal` or a `java.math.BigDecimal`).
- Additionally, it was using a private Avro constructor for `Decimal`,
which prevented proper conversion.
This PR addresses these issues with the following changes:
1. **Reordering in `tryUnpackValueWrapper`:**
- The `DecimalWrapper` case is moved before the `BytesWrapper` case. This
ensures that values written as decimals are unwrapped correctly.
2. **Enhancements to `deserialize`:**
- **ByteBuffer Handling:**
The conversion now uses Avro’s public factory method
(`org.apache.avro.LogicalTypes.decimal(precision, scale)`) to create a Decimal
logical type with the correct precision and scale.
- **Direct Decimal Values:**
The method now properly handles cases where the unwrapped value is
already a `scala.math.BigDecimal` or a `java.math.BigDecimal`. In both cases,
it enforces the target scale using `.setScale(dt.scale,
java.math.RoundingMode.UNNECESSARY)`.
3. **Unit Tests:**
- New unit tests have been added to cover:
- Decimal values unwrapped as a `ByteBuffer`.
- Decimal values unwrapped as a `java.math.BigDecimal`.
- Decimal values unwrapped as a Scala `BigDecimal`.
- Additionally, we reuse the existing utility method to generate a
DataFrame with decimals to ensure that our logic works correctly in an
integrated scenario.
### Impact
Decimal values retain their intended semantics when read from the metadata
table, ensuring that comparisons and filtering, and hence data skipping, based
on these values work correctly.
### Risk level (write none, low medium or high below)
low
### Documentation Update
_Describe any necessary documentation update if there is any new feature,
config, or user-facing change. If not, put "none"._
- _The config description must be updated if new configs are added or the
default value of the configs are changed_
- _Any new feature or user-facing change requires updating the Hudi website.
Please create a Jira ticket, attach the
ticket number here and follow the
[instruction](https://hudi.apache.org/contribute/developer-setup#website) to
make
changes to the website._
### Contributor's checklist
- [ ] Read through [contributor's
guide](https://hudi.apache.org/contribute/how-to-contribute)
- [ ] Change Logs and Impact were stated clearly
- [ ] Adequate tests were added if applicable
- [ ] CI passed
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